- H. o. FOLKINS ET AL 2,423,494 CRACKING OF HYDROCARBONS IN THE PBEsENCB OF HALOGENPCONTAINING SENSITIZER$.- } Filed ' Juné 11, 1945

Transcription

1 July 8, H. o. FOLKINS ET AL 2,423,494 CRACKING OF HYDROCARBONS IN THE PBEsENCB OF HALOGENPCONTAINING SENSITIZER$.- } Filed Juné 11, Sheets-Sheet} p-aurme DECOMPOSITION A I soon: INCREASE PRESSURE PERCENT 2 I 0 I IO II l2 l3l4l5 l6 l1- l8 l9 20 TIME (MINUTES) " , 1/6. 1 M H ~! ATTORNEY! -

2 ._ 2,423, July 8, H. o. FOLYKINS ET AL CRACKING OF HYDROCARBONS IN THE PRESENCE OF HALOGEN-CONTAINING SENSITIZERS Filed June 11, Sheeis-Shent 2 n-butane DECOMPOSITION AT 500 C nww awfuo... o, 5. Fiy. 2 I2. I TIME (MINUTES) Id - -. away??? INVENTORS 8. ac 81 _ BY. { ATIJIR/NEYWV

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4 Patented July- 8, ,423,494. _ UNITED stajt 1 This invention relates to cracking of hydrocar bons and is more particularly concerned with a _ method for converting higher boiling hydrocar bons into lower boiling hydrocarbons and for. making unsaturated hydrocarbons from satu rated hydrocarbons. > We have discovered that if thermal conversion of hydrocarbons is carried out in the presence of a. small amount of a poly-chlorinated aliphatic organic compound, particularly a poly-chlorin ated hydrocarbon of the para?in series in which some or all of the hydrogen atoms in the hydro carbon have been replaced by chlorine, admixed with a small amount of bromine or iodine or both, the cracking of the hydrocarbon is greatly ac celerated so that it is possible to obtain larger yields of, cracked hydrocarbons under the same time-temperature-pressure conditions than it is possible to obtain in thermal cracking of the hydrocarbons without sensitizer, and it is possi- ble to obtain yields at lower temperatures which are commensurate with yields obtainable at higher temperatures without sensitizers. Our in vention is applicable to either batch or continuous methods of cracking. In continuous, cracking methods by operating under usual thermal crack ing conditions in the presence of a sensitizer, not only can increased yields be obtained but higher 55 i PATENT- -<>FIF1 E7 I 2,423,494 CRACKING or nrnnocannons IN m I PRESENCE or nanocamconmmmq - K SENSITIZERS ~ Hillis 0. Folkins, Skokie, and Carlisle M. Thacher, Highland Park, 111., asaignors to The Pure Oil Company, Chicago, 111., a corporation of Ohio Application June 11, 1945, Serial No. 598,70 i In Canada February 24, \Claims./ (Cl ) octane gasoline can be produced.. By using a sensitizer, a larger throughput of charging stock 30 through a given size unit can be effected because of the acceleration in the cracking reaction I caused by the sensitizer. An object of our invention is to provide a method for conversion of hydrocarbons. Another object of our invention is to provide a method for accelerating cracking of hydrcar bons. Still another object of our invention is to pro vide a method for increasing octane number of 40 motor fuel made by cracking of hydrocarbons. A further object of our invention is to provide a sensitizer which will accelerate the decomposi tion of hydrocarbons.. _ A still further object of our invention is to pro 45 vide a method for improving thermal cracking of - hydrocarbons. I 1 Other objects of the invention will become ap parent from the following description and the ac companying drawings, of which Figure 1 is a graphical representation of data showing the unexpected results obtained from using a combination of bromine and chloroform as cracking sensitizer; Figure 2 is a graphical representation of data ~ _ showing. the unexpected results obtained from using a combination of bromine and propylene dichloride as sensitizer; and Figure 3 is a graphical representation of data showing the unexpected results obtained from using a combination of bromine and 1,2,3-tri chloropropane as cracking sensitizer. In accordance with the invention, a small amount of a poly-chlorinated aliphatic hydro carbon, such as chloroform, carbon tetrachloride, ethylene dichloride, propylene dichloride, and 1,2,3-trichloropropane, and bromine and/or iodine are mixed with the hydrocarbons subjected to decomposition. The poly-chlorinated aliphatic hydrocarbon and the halogen may be mixed with the hydrocarbons prior to charging them to the reaction zone or they may be injected directly into the reaction zone. The total sensitizer mix ture may be used in concentrations from ap proximately.055 mole percent to 5 mole percent based on the total charge and should contain not less than about..005 mole percent of bromine and/or iodine, and not less than aboutv.05 mole percent of poly-chlorinated aliphatic hydrocar bon. Higher concentrations of sensitizers may be used, but within the limits above set forth the reaction progresses rapidly without causing ac cumulation of undesirably large amounts of the sensitizers and their decomposition products in the motor fuel or other product which it is dee sired to produce. In our experimental workit has been found that a mixture containing from.03 mole percent of bromine up to 2 mole percent of bromine and from.25 percent of a poly-chlo- - rinated aliphatic organic compound up to 2 per cent of a poly-chlorinated aliphatic hydrocarbon gives unusually good results. When cracking hy drocarbon oils to gasoline boiling hydrocarbons, - it is preferred to keep the combined amount of catalyst below 1% by weight based on the oil cracked... The invention is useful in conjunction with conventional types of thermal cracking in which the hydrocarbons; are cracked at temperatures within the range of approximately 375 C. to 750 C. and is applicable to conversion of hydrocarbon gases such as propane and butane as well as to the conversion of liquid hydrocarbons such as, heavy naphtha, kerosine and gas oil. The com-, 50 bination of the bromine and/or iodine with a poly-chlorinated aliphatic hydrocarbon acceler ates the cracking reaction to an extent far in excess of that which would be expected from the additive e?ect of the poly-chlorinated aliphatic hydrocarbon and the bromine or iodine alone.

5 . In order to demonstrate this fact a number or runsv were made using normal butane as charg ing stock. The butane had a purity of 99%. The runs were all made in a Pyrex glass reaction ves sel at a temperature of 500 C. Before starting each run the reaction vessel was heated to the desired reaction temperature and then evacu ated by means 01 a vacuum pump to a pressure below mm. of mercury. Suiilcient butane in admixture with the desired amount oi v sensi tizer composition was then charged to the evac _ 2,420,404 4 ~ the end 01 the run. The?gures appearing in the table for 5% and 12.5% pressure increases were taken from curves of individual runs in which percent pressure increases were plotted 5 against time. In the table the?gures given un der the heading Time in minutes for AP of 25% are in some cases recorded and in other cases are interpolated from curves based on re corded pressures because in certain runs the 10 pressure rose above 25% increase too rapidly to obtain a reading at the exact point. Table > Tim" IZIZ QEB " 1 Sensitization rat-tom Products, Mole Per cent Run Na. 5 _ Name rim}. 0% 12.0% 20% 0% 12.0% 20% 00, m Residue i : g ; g kg n4 as ?: _ % o g % of? b 7a 7. L a a % %: o a Gig-(51:33:: 0% Average 012 or more runs. Buns 5-12, CHOh is chloroform. Runs 14-21, 01300]; is progylene dichloride. Runs 23-26, in,2, trichlor propane. I _ uated vessel until the pressure in the vessel ap proximated atmospheric pressure. The reaction was permitted to proceed. in the closed reaction vessel while the temperature was maintained at 500 C. until a pressure increase of 25 percent above the initial pressure was observed. where upon the reaction gases were rapidly removed from the reactor and analyzedn In some runs where the accelerationin reaction was extremely rapid the pressure increase somewhat exceeded 25 percent before the reaction was terminated. A number of runs were also made without any sensitizer and other runs were made using only a poly-chlorinated para?ln and only bromine as sensitizer. In each of the runs the initial pressure was calculated, a pressure reading was made 0.5 minute after the run began, thereafter pressure readings were made at intervals of 1 minute from the beginning or the run until 6 minutes thereafter, from that point readings were made at 2 minute intervals until 20 minutes after the run began, and when it was necessary to run in excess or 20 minutes to obtain 25% pressurein crease, readings were taken at 5 minute inter vals during the period from 20 to 40 minutes and vat l0 minute-intervals beyond 40 minutes until 75 tion factor or The sensitization factors recorded in the table 50 are obtained by dividing the time required for a particular pressure increase without.sensitizer by the time required for the same pressure increase with sensitizer. By referring to the table. it is evident that 55 chloroform, propylene dichloride and 1.2,3-tri chloropropane alone sensitize the cracking of butane to some extent. The table also shows that bromine is a more active sensitizer than the chlorinated hydrocarbons. However, by using a 00 combination of bromine with a poly-chlorinated hydrocarbon, the sensitizing eifectv is much greater than can be anticipated from the addi tive effect of the chlorinated hydrocarbons and bromine when used alone. In fact, the mixture 05 of a small amount of a poly-chlorinated hydro carbon with bromine will increase the sensitiz ing effect of the bromine far. above the value which an amount of bromine equivalent to the combined amounts of bromine and chlorinated 70 hydrocarbon gives. For example. one-half per cent of bromine (run 3) vgave a sensitization fac tor for 25 percent pressure increase,of 6.2; whereas,.25 percent of bromine mixed with.25 percent of chloroform (run 8) gave a sensitiza Similarly, 0.25 percent of

6 . H5. bromine mixed with 0.25 percent of propylen dichloride (run 17). gave a sensitization factor for 25 percent pressure increase of 12.8, as against 6.2 for one-half percent of bromine. A mix ture of bromine and l,2,3,-trichloropropane in amounts of.25 percent each (run 24) gave a sensitization factor of 10.4 as against 6.2 for one-half percent of bromine. Thus, it is ap parent that the poly-chlorinated hydrocarbons which are poorer sensitizers than bromine when used alone, enhance the sensitization eifect of bromine when mixed therewith to an extent con siderably above that of an equivalent amount of bromine alone. In order to further demonstrate the remark able enhancement in sensitization obtained by using a mixture of bromine and poly-chlorinat ed aliphatic hydrocarbon. curves were plotted for several runs with time in minutes as ab scissae and pressure increase as ordinates. Referring to Figure 1, curve I is a curve for the average of several blank runs, data for which is given in the table under run No. 1. Curve 2 is the curve based on data recorded for run No. 2. Curve 3 is the curve for data recorded in run No. 5. Curve 4 represents the hypothetical or additive results which would be expected from using a mixture, of.25 mole percent of chloro form and.25 percent of bromine as sensitizer, and is obtained by adding the pressure increase without sensitizer at a selected time (from curve. I), the pressure increase over that of the blank run caused at the same time by the presence of chloroform alone (curve 3 minus curve I) and the- pressure increase oausedat the same time by the presence of bromine alone (curve 2 minus curve I), and plotting on the graph the?gures obtained for a su?icient number of different time _ periods to be able to draw a curve through the points. As an example, referring to Figure 1, at a time approximately 7 minutes after the be ginning of the run, pressure increase without any sensitizer (obtained from curve I) is 4.8 per cent. At the same time the pressure increase in the run sensitized by chloroform alone is 7.5 percent (obtained from curve 3) and the pres sure increase in the run sensitized by bromine. alone is 14.7 (obtained from curve 2). Pressure increase due to the. presence of chloroform is therefore, 7.5 minus 4.8 or 2.7 percent. Pressure increase due to the presence of bromine is, there fore, 14.7 minus 4.8 or 9.9 percent. The pres sure increase that might be expected from the combination of chloroform and bromine at a time seven minutes after the run begins is the. sum of the pressure increase at the same time without sensitizer and the pressure increases caused by each of the sensitizers or 4.8 plus 2.7 plus 9.9 or 17.4 percent. By referring to curve 4, it will be seen that 7 minutes after the run begins the pressure increase is approximately 17.4 percent. 5. Curve 5 represents the actual experimental data obtained in the run using the combination sensi; tizer. At a period 7 minutes after the run began, it will be seen that the actual pressure increase was 25 percent as against an expected increase of 17.4 percent. Considering the effect in another way, in order to get a pressure increase of approximately 25 percent, it was necessary to permit. the reaction to continue for a period of 7 minutes, whereas from the additive results of theindividual sensié tizers, this pressure increase would not have been 2,425, expected v until the reaction had continued forv approximately 13 minutes. Referring now to Figure 2, the curves are sim ilar to those in Figure 1, with the exception that the data.are recorded in connection with a mix ture of bromine and propylene dichloride. As is apparent from the curves, the sensitization factor of a mixture of bromine and propylene dichloride in amounts of.25 percent each is even greater than that of the mixture of bromine and chloro form. The same is true for the mixture of bro- " mine and 1,2,3-trichloropropane, results of which are shown graphically in Figure 3. In order to further demonstrate the effective ness of mixtures of bromine and poly-chlorinated aliphatic hydrocarbons in the sensitization of hy drocarbons, Pennsylvania gas oil was subjected to cracking in a continuous laboratory cracking apparatus at 525 C. under approximately atmos 75 pheric pressure at a through-put of approximate ly 165 grams of charging stock per hour. In a run in which no sensitizer was used, using a once through operation, 10.7 percent by weight of gas oil was converted to liquid hydrocarbon boiling below 400 F. and 6.2 percent by weight was con verted to gas. Under similar conditions using a mixture of percent by weight of bromine and 0.5 percent by weight of propylene dichloride, 14.8 percent by weight of the gas oil was con verted to liquid hydrocarbon boiling below 400 F. and 9.1 percent by weight of the gas oil was converted to gas. Under the same conditions a. mixture of percent by weight of bromine and 0.5 percent by weight of 1,2,3-trichloropropane converted 15.6 percent by weight of the gas oil to liquid hydrocarbon boiling below 400 F. and 9.7 percent by weight of the gas oil to gas. From the analyses of the reaction products appearing in the table, the reaction is predomi nantly one of splitting the carbon to carbon bond as shown by the relatively large amount of un saturated hydrocarbons formed and the small amount of hydrogen formed in the reaction. The nature ofthe reaction products obtained is essen tially the same regardless of whether or not sensi tizer is used. The invention is useful in connection with known types of mineral oil thermal cracking with out catalyst. It is also useful in catalytic crack-v ing operations wherein a known solid comminuted catalyst, such as natural or synthetic alumina silica compositions, is used. The invention may also be used in connection with cracking of gases to make unsaturated hydrocarbons, such as crack ing of propane to ethylene, cracking of butane to ethylene and propylene or the cracking of liquid hydrocarbons to ole?ns or diole?ns such as buta diene.. Wherever the terms poly-chlorinated aliphatic hydrocarbon or poly-chlorinated para?in areused, they are intended to include compounds in which all hydrogen has been replaced by chlorine atoms, as for example, carbon tetrachloride, hexachlor ethane and octachlorpropane. This application is a continuation-in-part of ouryapplication Serial No. 521,596,?led February 9, 1944, entitled Hydrocarbon conversion. It is claimed: 1. The method of cracking hydrocarbons,com- prising subjecting hydrocarbons to suitable crack. ing conditions of time, temperature and pressure in the presence of a small amount of a halogen selected from the group consisting of bromine and iodine and a small amount of a poly-chlorinated aliphatic hydrocarbon.

7 7 > v ; 2. Method in accordance with claim 1 in which the halogen is bromine and the poly-chlorinated aliphatic hydrocarbon is a poly-chlorinated par 3. Method in accordance with claim 1 in which the amount of halogen present is at least.005 mole percent and the amount of poly-chlorinated aliphatic hydrocarbon is,..at least.05 mole per cent. 4. Method in accordance with claim 1 in which the minimum amount of halogen and poly-chlo rinated aliphatic hydrocarbon present is about.005 and.05 mole percent, respectively, and the maximum combined amount of the two is about 5 mole percent. 5. The method 01 cracking hydrocarbons con,taining at least 3 carbon atoms per molecule com prising subjecting said hydrocarbons to, temper ature of approximately 375 to 750 C. in the presence of asmall amount of bromine and a poly-chlorinated aliphatic hydrocarbon. 6. Method in accordance with claim-5 in-which the poly-chlorinated aliphatic hydrocarbon is 1,2,3-trichloropropane. 7. Method in accordance with claim 5 in which the poly-chlorinated aliphatic hydrocarbon is chloroform. 8. Method in accordance with claim 5 in which the poly-chlorinated aliphatic hydrocarbon is propylene dichloride Method in accordance with claim 5 in which 2,428,494 _ the bromine is present in an amount ofapproxi- _ mately.03 to_ 2 mole percent and the poly- chlorinated hydrocarbon is present in amounts or approximately 0.25 to 2 mole precent The method of cracking C4 hydrocarbons comprising subjecting said hydrocarbons to tem peratures of the order of C. in the presence of small amounts of bromine and a poly-chlorinated aliphatic hydrocarbon. 11. Method in accordance with claim 10 in which the amount of bromine is not less than.005 mole percent and the amount 01 poly-chlo 18 so 40 rinated. aliphatic hydrocarbon is not less than -.05 mole percent and the maximum combined amount of, the two is about 5 mole percent. 12. Method in accordance with claim 5 inwhich the hydrocarbons are normally liquid hydrocar bone The method of "cracking hydrocarbon/oil comprising subjecting said oil to temperatures within the range of approximately 375 to 750 C. in the presence of a mixture of bromine. and a, poly-chlorinated aliphatic hydrocarbon, the bro-. mine. being present in amount not less than.03" mole per cent and the polychlorinated ali- phatic hydrocarbon being present in an amount not less than 0.25 mole per cent, thecombined amount of the bromine and polychlorinated ali phatic hydrocarbon being less than 1% by weight of the oil Method in accordance with claim 13 in 20 which the amount of bromine is about % by weight of the oil and the amount of polychlorin ated aliphatic hydrocarbon is about 05% by weight 01. the oil Method in accordance with claim 13 in 25. which the polychlorinated aliphatic hydrocarbon is 1,2,3-trich1oropropane. 16. Method in accordance with claim 13 in which the polychlorinated aliphatic hydrocarbon is propylene chloride. _ - HILLIS O. FOLKINS. CARLISIE M. THACKER.. REFERENCES crren The following references are of record in the file of this patent:..1 ~ UNITED STATES PATENTS Number Name Date 2,221,952 Pier et a1. Nov. 19, ,925,421 Van Peski Sept. 5, ,122,903 Winkler.._- July 5, ,063,133 Tropsch -n -_ Dec. 8, ,213,345 Marschner Y Sept. 3, 1940